# Laser Temp

I was chatting with a friend about laser cutting. Googled for a while - didn’t find the answer. I am wondering if anyone can give approximate temperature of a 40-45 Watt laser at it’s focal point - I am sure there is tons of math and complicated answers (very fair, and expected). But I am looking for a general answer (if one exists). Thanks!

This really depends on the material the laser is pointed at. A Watt is an amount of energy per second.

Temperature change will depend on many factors including the material’s ability to absorb the wavelength of light transmitting the energy, the materials ability to dissipate the heat(high for most metals) and the energy required for phase change(liquid to gas/solid to liquid/solid to gas) if there is any.

You can think of it similarly to microwave ovens commonly in the 1000 Watt to 1500 Watt range. It’s not can it boil water it’s how many seconds will it take to boil water.

This rolls back to the benefit of Glowforge providing materials. When you put them into your Glowforge it will recognize the material and be able to know how fast and how strong to drive the laser to perform what you want on it.

Yep and just like a magnifying glass on a sunny day a spot location(so if the laser is not moving or is moving slow) will get hotter over time. It is safe to put your hand in the focal point of the magnifying glass for a split second.

I may be wrong but I believe a laser itself although it has energy it has no heat(vibration of physical particles) and this energy is transferred to the material and surroundings as heat based on the properties of that material. So unfortunately there is no solid answer, off the top of my head from school wood burns at about 400degrees C so the laser can easily achieve more than that.

@jacktyler_co_uk - seems you are right

Finally found this:

Interesting notes on laser technology

Heat is the random motion of matterparticles (atomic or molecular particles) – however, the laser beam itself is not made of matter but of ‘photons’, the so-called ‘light particles’ which have no mass, i.e. that a laser beam can have no temperature.

A CO2 laser beam, as an electro-magnetic ‘light wave’ at a frequency of 10,600 microns, contains a certain energy which is (partially) absorbed by the material. The photons, i.e. the ‘light particles’, transfer their energy to the atomic or molecular structure of the material, which in turn causes the material to heat up. If the energy of the laser is high enough and is allowed to work for long enough, the temperature required to vaporise the substance develops on the material.

Just a minor correction: it’s not frequency, but wavelength, and it’s nm (nanometers), or equivalently, millimicrons, not microns.

Also: 10600 nm is absorbed particularly well by organic (in the chemical, not ecological sense) materials like acrylic and wood, and exhibit total internal reflection, so you get better penetration and smaller kerf. Part of why we use CO2 instead of diodes, fiber, or YAG.